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On Wed, 19 Aug 2020 10:48:30 -0600, Dan Marotta
wrote: Remember your high school chemistry (or was it physics?).* Water gives up 1 calorie per gram per degree C while cooling.* To transition from water at zero deg C to ice at zero deg C requires the loss of 80 calories per gram per degree C.* That's a lot of heat to be lost!* Sure, you have a large surface area, but you have a very large volume as well.* It would take quite some time to freeze a ballast tank. Bottom line is I never worried about icing the ballast tanks (when I had them) at sub-freezing temperatures.* Now freezing the dump valves is a different issue, but not really if you fly your glider all the way to a stop.* I once landed my LAK-17a with nearly 50 gallons on board and didn't notice until after getting out of the glider.* Another time, one dump valve stuck closed and, again, I landed with 25 gallons in one wing and empty in the other.* I didn't notice until coming to a stop and the full wing dropped heavily. .... text deleted Maybe off topic, but what worried me in past years when I flew in the New Mexico mountains was not the wing ballast tanks, but the tail tank. I always had visions of the tail tank freezing and failing to dump when I dropped ballast, leaving my CG too far aft. I usually left the tail tank empty if I was expecting high altitutes. Bob |
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I fly NM with water regularly, both in the wings and the tail. I generally fly dry in the early spring when temperatures are still sub freezing at 17,000+ and start filling up during the summer. No problems so far, but if I do decide to use water in the tail tank when it's really cold, I can always add some propylene glycol antifreeze. Several of our more manic pilots do that and it seems to work well.
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On Wednesday, August 19, 2020 at 8:03:49 PM UTC-7, wrote:
I fly NM with water regularly, both in the wings and the tail. I generally fly dry in the early spring when temperatures are still sub freezing at 17,000+ and start filling up during the summer. No problems so far, but if I do decide to use water in the tail tank when it's really cold, I can always add some propylene glycol antifreeze. Several of our more manic pilots do that and it seems to work well. Not telling you what to do but in the Truckee/Minden area it is routine to fill the tanks and fly all day at sub freezing temps - probably 4 - 5 hours below freezing. We did have one case of the tail tank dump valve on a DuoDiscus leaking, which dribbled water onto the rudder hinge and controls, which froze the rudder in position. Pilot flew carefully home on a 200 mile final glide, descending through warmer temps and it melted enough to break loose. |
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